Posts Tagged: fuel trim
Fuel Trim: What the numbers mean
Fuel Trim Explained: What the numbers mean and how to use the data to diagnose your engine Quick Summary: Fuel trim in an OBD-II vehicle is the engine computer’s ongoing adjustment of fuel injector duration to keep the air-fuel mixture as close as possible to the ideal 14.7:1 ratio. Using feedback from the oxygen sensors, the ECM monitors whether the engine is running rich (too much fuel) or lean (too much air) and instantly alters short-term fuel trim (STFT) to correct the mixture. In contrast, long-term fuel trim (LTFT) stores … Read More
Understanding the Fuel Trim System
The Fuel Trim System Explained: Optimizing Your Engine’s Fuel Delivery Modern automotive computers use fuel trim to vary the fuel provided to the engine based on a FEEDBACK STRATEGY that compensates for wear and tear on the engine and fuel delivery components and sensor degradation. In other words, the computer receives feedback information from many different sensors to inform the computer how good of a job it did in calculating how much fuel to add to the incoming air. The computer then adds or subtracts fuel during the next injection … Read More
Top Causes of the P0171 Code and P0174 Code
Fix a P0171 and P0174 Lean Code Using Proven Diagnostic Strategy Quick Summary The P0171 and P0174 codes are some of the most misunderstood OBD-II trouble codes. Both codes indicate the engine is running too lean—either too much air or too little fuel. A P0171 indicates a lean condition on bank 1, while a P0174 indicates a lean condition on bank 2. Most of the time, these codes are caused by something simple, such as a vacuum leak, a dirty MAF sensor, or low fuel pressure. But I’ve also seen … Read More